Vehicle body assembly

ABSTRACT

An assembly of vehicle body members by injecting an adhesive into a predesigned channel cavity formed at the joint interface of the vehicle body members.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of pending application Ser. No.08/326,908, titled "Vehicle Assembly Method" filed Oct. 21, 1994 by thesame inventors as in the present application.

FIELD OF THE INVENTION

The present invention generally relates to a vehicle body assembly andmore particularly, relates to vehicle body members assembled byinjecting an adhesive into a predesigned channel cavity formed at thejoint interface of two vehicle body members.

BACKGROUND OF THE INVENTION

Automobile body panels and frame members are assembled together byvarious assembly methods. For instance, conventional sheet metal bodymembers are welded together by spot welds or fastened together bymechanical means. In recent years, polymeric based composite vehiclebody members are widely used. Adhesives have been found useful in theassembly of plastic body members. Such applications include the bondingof a body panel to a frame member, i.e. the bonding of an appearancepanel to a support structure such as in the application of a vehiclehood, or a variety of other body components. However, most of theadhesive bonded parts are used in non-structural applications.

To qualify as a bonding method for automobile body components, variousperformance requirements must be met by the adhesive bonded assembly.Such requirements include, for instance, an exposure test of automobileservice environment for low temperature/high temperature, salt spray,vibrations, weatherability, etc. In the case of a structural component,the additional requirements for the component to carry a dynamic: loadand to survive various stress and fatigue conditions must also be met.Due to the difficulty of meeting all these requirements, the adhesivebonding technique has not been widely used in the assembly of automobilestructural components.

It is therefore an object of the present invention to provide structuralcomponents of a vehicle bonded by adhesives that does not have theshortcomings of the prior art methods.

It is another object of the present invention to provide vehiclestructural components bonded by adhesives where the components can beassembled together in a dry state without contamination by squeezed-outadhesives.

It is a further object of the present invention to provide vehiclestructural components adhesively bonded together in such a way that thevehicle components may be disassembled before the application of theadhesive.

It is yet another object of the present invention to provide vehiclestructural components which can be adhesively bonded together which canbe carried out efficiently in, an automobile assembly line environment.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method of adhesively bondingvehicle structural components together neatly without the need ofcleaning up messy adhesives can be carried out.

In the preferred embodiment, a special V-shaped tongue-and-groovechannel cavity is provided at the interface of the two vehiclestructural components to accept the adhesive. The tongue-and-groovechannel is designed such that the shoulders of the tongue and theshoulders of the groove have an interference area so as to provide afluid-tight seal of the channel cavity formed between the tongue and thegroove from the outside environment. An adhesive is injected through aninjection gate to fill the cavity formed between the tongue and thegroove until the adhesive reaches the end of the cavity which is vented.The viscosity of the adhesive and the pressure drop of the adhesive flowcan be predetermined so as to provide a suitable fill time for thecavity.

In an alternate embodiment, a vacuum or a negative pressure is firstpulled from the vent hole situated at the end of the cavity such thatthe intimate mating of the two frame members can be enhanced andfurther, the flow rate of the adhesive can be improved.

In other alternate embodiments, the cross-sectional areas of the channelcavity between the two frame members to be bonded together areconstructed in other than tongue-and-groove configurations. Forinstance, a right-angle joint provides the benefit of high shear andhigh tensile strength regardless from which direction the joint isloaded. In another tongue-and-groove arrangement, the shoulder areas ofthe tongue and the groove are not interfering with each other, instead,a seal made of a suitable sealing material is used to contain theadhesive under pressure inside the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent upon consideration of the specification and the appendeddrawings, in which:

FIG. 1A is the front view of a typical vehicle upper and lower bodyshells that are suitable for the present invention bonding technique.

FIG. 1B is a perspective view of the vehicle upper and lower shellsshown in FIG. 1A.

FIG. 2A is the top view of a vehicle dash structure.

FIG. 2B is a sectional view taken along line BB, of FIG. 2A.

FIG. 2C is an enlarged view of the tongue-and-groove channel cavitybetween the upper body shell and the lower body shell shown in FIG. 2B.

FIG. 3A is an enlarged cross-sectional view of a right-angle joint.

FIG. 3B is an enlarged cross-sectional view of a variation of thetongue-and-groove joint.

FIG. 3C is an enlarged cross-sectional view of another variation of thetongue-and-groove joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides an assembly of vehicle body componentsadhesively bonded together by providing a special joint having a channelcavity for the injection and flow of adhesives at the interface betweenthe two body members.

Assemblies according to the present invention may include bondedpolymeric composite components of a vehicle body. The polymericcomposite components for a vehicle body are used frequently to achievethe goal of maximum parts consolidation and cost savings. The presentinvention can also include vehicle body components that are made ofconventional sheet metal materials. An adhesive of a specific chemistrymay be selected for each application as long as the adhesive providesadequate bond strength to the surfaces joined together.

The present invention may utilize a low pressure injection apparatus forinjecting an adhesive through an injecting port into a channel cavityformed in the joint interface. The injection process is stopped afterthe channel cavity is completely filled, i.e. when the adhesive reachesthe end of the cavity by popping out an indicator. Prior to theinjection of the adhesive, the body components may be held together bymechanical devices such as bolts so that the injection process of theadhesive can be easily carried out.

The adhesive bonding method provides several advantages. First, thevehicle body components are put together initially in a dry state, i.e.,prior to the injection of the adhesive, and therefore there is noadhesive squeeze-out problem and messy adhesive to clean up. This isimportant in a manufacturing environment where valuable production timeis frequently lost in the clean up of excess adhesives. Secondly, theadhesive bonding method affords the capability of disassembling thevehicle body components before the adhesive is applied. This reduces thenumber of scrap parts due to misalignment of the assembly or otherassembly defects. Thirdly, in the process, an adhesive is applied by alow pressure injection device and flows continuously until a pop-outindicator is ejected at the end of the channel cavity (i.e., at the venthole). The injection pressure is then immediately stopped so that thereis no excess adhesive to be cleaned up and furthermore, there is nowaste of adhesive materials.

Referring now to FIG. 1A, a modular design vehicle body 10 according tothe present invention bonding is shown with an upper body shell 12 and alower body shell 14 to be bonded together. This is a typical compositevehicle body shell that is being considered by the automotive industryfor ease of manufacturing and assembly. It is sometimes referred to as a"shoe box" construction of a vehicle body. FIG. 1B shows a perspectiveview of FIG. 1A.

FIG. 2A is the top view of a dash structure 40 used in a vehicle. Aninjection port 22 is provided at the center of the dash so that an equalamount of adhesive flow can be directed to both directions to firstreach the ends 24 and 26 and then reach vent holes 28 and 30. When thevent holes 28 and 30 are reached by the adhesive flow, the completechannel cavity 32 is filled. A cross-sectional view taken along line BBin FIG. 2A is shown in FIG. 2B. Also shown in 2B is a plenum structure20 which mates with the dash structure 40. A detailed enlargedcross-sectional view of the joint between plenum 20 and dash 40 is shownin FIG. 2C. It is seen that a tongue-and-groove joint is providedbetween the upper plenum structure 20 and the lower dash structure 40.The tongue 42 and the groove 44 fit together forming a channel cavity 46for the adhesive flow. The shoulder 48 of tongue 42 on the plenumstructure 20 is designed such that it provides a 0.5 mm interferencewith the shoulder 50 of the groove 44 located on the dash structure 40.This interference provides a fluid tight seal for the channel cavity 46during the time when adhesive is pumped into the channel and filling thechannel cavity under low injection pressure. Other sealing methods canalso be used to produce the same desirable result.

It should be noted that joint constructions other than tongue-and-groovecan also be used in the present invention. One of such jointconstructions is shown in FIG. 3A as a right-angle joint. An upper framemember 52 and a lower frame member 54 are joined together at theshoulder portions 72 and 74 of the lower frame member 54 forming achannel cavity 56. The benefit of such a right-angle joint is that itcombines the desirable shear and tensile properties together such thatno matter from which direction force is applied to the joint, the jointexhibits a maximum strength.

Another variation of a tongue-and-groove joint is shown in FIG. 3B. Anupper frame member 58 and a lower frame member 60 are joined together atthe shoulder portions of 76 and 78 of the lower frame member 60 forminga channel cavity 62 for filling of an adhesive . This tongue-and-groovearrangement also provides a maximum surface area for improved bondstrength. FIG. 3C shows yet another variation of the tongue-and-groovejoint construction wherein the shoulders of the upper body member 64 andthe lower body member 66 are not in contact. In order to pull vacuum inthe flow channel and to prevent leaking of the adhesive from the channelcavity, seals 68 made of a suitable sealing material are used betweenthe mating surfaces of the upper member 64 and the lower member 66. Asuitable material for the seal is buytl rubber which is frequently usedin the sealing of automobile bodies members 64 and 66 may be furtherjoined via bolts 71 with nuts 73 if desired.

The volumetric flow rate of an adhesive through a channel cavity can becalculated by the following equation. ##EQU1## wherein Q is thevolumetric flow rate, /P is the pressure drop, B is the slit halfthickness, L is the slit length, W is the slit width, and / is the fluidviscosity. Since the thickness of the slit is defined as 2B, when achannel is 2 mm thick, B is equal to 1 mm. In a typical example, achannel width of 26.2 mm, a B value of 1 mm, and a channel length of 2 mare used. Assuming that a desirable fill time for the channel cavity is1 min., using the channel dimensions indicated along with the 1 min.fill time, a volumetric flow rate of approximately 1,750 mm³ /sec isneeded to fill the channel cavity shown in the example. The relationshipbetween the pressure drop required to pump the adhesive through thechannel cavity and the viscosity of the adhesive can therefore bepredicted.

A typical adhesive that can be used is a two-part polyurethane adhesive,such as that supplied by the Ashland Chemical Company under thetradename of Pliogrip®. Typical viscosities for this adhesive is between16 and 18 Pa•sec. An adhesive having a viscosity in this range requiresa pressure drop of approximately 500 psi to fill a channel cavity of 2mm thick.

It was discovered that flowability and pumpability are major criteria tobe satisfied for a satisfactory adhesive application. For an adhesivehaving a low viscosity, i.e., in the range of 1-2 Pa•sec., an inletpressure between 30 and 60 psi to fill the desired channel within 1 min.time is required. When the thickness of the channel is doubled from 2 mmto 4 mm, the channel volume also doubles and therefore requires thedoubling of the pumping rate. It is advantageous to use a thickerchannel in order to minimize the pressure drop required for pumping theadhesive. The pressure drop required to pump a prepolymer at variousflow rates can be measured by using a pressure gage. The prepolymer canthen be tested on a cone-and-plate rheometer to determine its viscosity.

It was discovered that an ideal length of the tongue in atongue-and-groove joint construction shown in FIG. 2C is approximately15 mm. This affords a larger surface area for the adhesive to be bondedto the body members and allows greater load transfer capability betweenthe upper and the lower body shells.

It has been observed that the failure mode of a joint having sufficientlength of the tongue is a tensile failure in the body member itself asopposed to a shear failure in the adhesive bonded joint.

While the present invention has been described in an illustrativemanner, it should be understood that the terminology used is intended tobe in a nature of words of description rather than of limitation.

Furthermore, while the present invention has been described in terms ofseveral preferred embodiments thereof, it is to be appreciated thatthose skilled in the art will readily apply these teachings to otherpossible variations of the invention. For instance, any one-part ortwo-part adhesive materials other than the polyurethane adhesive, i.e.,epoxy, vinyl ester, etc. can also be suitably used to achieve the samedesirable results of the present invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

What is claimed is:
 1. A vehicle body assembly bonded together by anadhesive comprising:a first vehicle body part having a first surfacecomprising a protruded area, a second vehicle body part having a secondsurface comprising an indented area, a channel cavity formed by saidprotruded area in said, first surface and said indented area in saidsecond surface, said cavity being filled with an adhesive bonding saidtwo vehicle body parts together.
 2. A vehicle body assembly according toclaim 1, wherein said channel cavity having the shape of atongue-and-groove.
 3. A vehicle body assembly adhesively bonded togetherby a method comprising the steps of:providing a first vehicle body parthaving a first surface to be bonded to a second vehicle body part, saidfirst surface having a protruded area, providing a second vehicle bodypart having a second surface to be bonded to said first vehicle bodypart, said second surface having an indented area positionedcorresponding to the position of said protruded area on said firstsurface, positioning said first and said second vehicle body partstogether in a bonded position such that a channel cavity is formed bysaid protruded area on said first surface and said indented area on saidsecond surface, and injecting an adhesive into said channel cavity whilesaid first and second vehicle body parts are positioned together in saidbonded position and forming an adhesive bond between said first and saidsecond vehicle body parts.
 4. A vehicle body assembly according to claim3, wherein said channel cavity has the configuration of atongue-and-groove shape formed by a tongue in said protruded area insaid first surface and a groove in said indented area in said secondsurface.
 5. A vehicle body assembly according to claim 3, wherein saidpositioning step further comprises fastening said first and said secondvehicle body parts together by mechanical means.
 6. A vehicle bodyassembly according to claim 5, wherein said mechanical means comprisesbolts.
 7. A vehicle body assembly according to claim 3, wherein saidadhesive is injected into said channel cavity through an injection portin fluid communication with said channel cavity.
 8. A vehicle bodyassembly according to claim 3, wherein said channel cavity connects withat least one aperture in fluid communication with the outsideenvironment at a location farthest away from said injection port.